1. Field of the Invention
This invention relates to laser compositions which significantly increase the efficiency of chromium/thulium/erbium-doped garnet lasers and permits improved output at lower wavelengths than previously known for this type of laser.
2. Prior Art
Chromiumlthulium/erbium("CTE")-doped garnet lasers are known in the art and have found utility in a variety of applications. Similarly, the existence of numerous Er.sup.3+ energy state transitions is well known. In particular, previous workers in the art have learned that lasing at an IR frequency of 2.95.mu. involves the transition .sup.4 I.sub.11/2 to .sup.4 I.sub.13/2 and Stark levels X.sub.2 to Y.sub.7. This transition results in reasonably efficient laser action at room temperature when the erbium concentration in the garnet host, preferably YAG, exceeds about 30% of the yttrium sites. However, while the 2.96.mu. wavelength laser is an excellent tool for medicine and various other applications related to the oxygen-hydrogen bond stretching vibration of water molecules, it has one very serious shortcoming: it cannot be efficiently transferred via common silica fiber. It is advantageous for practical use of lasers to deliver the laser beam via an optical fiber. Most common optical fibers are made from silica, or phosphate glass compounds, but their performance is limited to a maximum wavelength of about 2.8.mu.. The laser beam with wavelength of 2.95.mu. must therefore be delivered via sapphire or fluoride fibers, which are not yet perfected and are more costly. A laser operating at about 2.7.mu., preferably at room temperature, with sufficient power would offer numerous benefits for most medical applications, as well as the many related applications.